One of the general application principles of an optical scanner is that a light beam is reflected through a light-path device and formed into an image by a lens and, a charge-coupled device is further applied to convert the light signal into digital signal capable of being memorized and processed by a computer. However, since the limitation of a certain light-path's length is required to form the desired image, the light has to be reflected several times by a plurality of reflection mirrors in the light-path device to effectively reduce its dimension. Therefore, in the light-path device, the number, the size, and the inter-corresponding arrangement and position of the reflection mirrors will decide the light-path route of a light-path device and, in addition, help match with the functions of magnification and reduction of a lens to determine the length of the light-path.
Please refer to FIG. 1, which is a three-dimensional structural illustration for a flatbed optical scanner typically seen in the current market. An object supporting glass 16 is arranged on the upper side surface of an outer shell 11 of a scanner 1 for placing a reflective object 10. A light-path device 2 is driven by a driving device 13 for proceeding in a linear motion along the direction of a guiding rod 14 in the hollow outer shell 11, such that an image scanning job is executed on the reflective object 10 placed on the object supporting glass 16.
Please refer to FIG. 2, which is an illustration for the light-path route in a flatbed optical scanner according to the current prior art. The route of the light-path is determined by the light-path device 2, which is comprised of light source 20, light-path module 21, and charge-coupled device 22. The light-path module 21 includes three reflection mirrors 211, 212, 213, and a lens 214. The light of the light source 20 penetrates through the object supporting glass 16 irradiates upon the reflective object 10. The light irradiated from the reflective object 10 is then reflected sequentially by the first reflection mirror 211, the second reflection mirror 212, and the third reflection mirror 213, which finally reflects the light to a lens 214, from which the focused light is further irradiated to a charge-coupled device 22.
To reduce an object plane in the prior art described above in order to fit the image of the reflective object 10 on the charge coupled device 22, magnification and reduction functions of the lens may be altered. However, because of the limitations associated with the specification and physics of the lens itself during manufacture and the size of the scanned object itself, the length of the light-path route must be designed to be long enough to fit the image of the entire scanned object 10 on the lens. Hence, improvements in the adjustability of the light-path device in order to adjust the length of the light path is needed.